1. Field of the Invention
This invention is related to a boom assembly for a work machine used for a front end loading and a backhoe loading for the work machine.
2. Description of Background Art
A boom assembly with a reinforced torsional strength is disclosed which has the minimum effect of the strength of the boom and arm in other working modes, for example, as set forth in the specification of the U.S. Pat. No. 3,254,780, the specification of the U.S. Pat. No. 4,155,470 and the specification of the U.S. Pat. No. 4,161,369.
In the above mentioned conventional techniques, a box type boom arm is formed by overlapping an inward facing channel and outward facing channel having horizontal and vertical planes which are welded along adjoining edges. The boom arms are joined by a pair of cross tie members.
As the welding line of the adjoined edges is formed along the whole longitudinal direction of the upper and lower faces of the boom, it was very difficult to maintain the box type for a long period.
Namely, the welded parts which have the welding lines both in the upper and lower faces of the boom were easy to separate due to the repetition of tensile and compressive stresses, above all, torsional stress by the loading work of the boom.
Further, the weld presented a bad appearance which is a factor causing a lower value of the commodity by having the welding lines both in the upper and lower faces of the boom, even if the booms were finished by painting.
Moreover, as the boom arm has an inflecting part, it was very difficult to manufacture a pair of the inward and outward facing C-channels in one piece having an inflecting part.